/**
 * @author yexiebao
 * @date 2025/5/15
 */
public class DoubleListNode {
    //双链表
    private class ListNode{
        int val;
        ListNode prev;
        ListNode next;
        public ListNode(){}
        public ListNode(int val){
            this.val = val;
        }
        public ListNode(int val, ListNode prev, ListNode next){
            this.val = val;
            this.prev = prev;
            this.next = next;
        }
    }

    private ListNode head;
    private ListNode tail;
    private int size;
    public DoubleListNode(){
        head.next = tail;
        tail.prev = head;
        size = 0;
    }
}